The popular programs, designed primarily to provide health care coverage and income security for seniors, have been politically untouchable for decades.
But presumptive GOP presidential nominee Mitt Romney, as well as most congressional Republicans, embrace sweeping changes that, among other things, would alter dramatically how seniors get health coverage a decade from now.
Democrats think the GOP has given them a gift, an issue they can use to illustrate how Republicans and their well-heeled friends are ready to abandon generations-old societal obligations to seniors.
But it's not clear who's got the political advantage, if any. The major GOP Medicare plans wouldn't affect anyone now 55 and older, and those younger than that age may care more about arresting the ballooning federal debt -- and Medicare's impact on it -- than the health of the program decades from now.
Study after study has found that to pare the government's record debt significantly, the ever-rising costs of Social Security and Medicare must be slowed. Social Security and Medicare accounted for 36 percent of federal spending in fiscal 2011, and as baby boomers age, those costs are projected to keep rising.
Polls show that the economy is the primary voter concern in the 2012 elections, but these two giant entitlement programs are part of the economic equation.
Still, even suggesting tinkering with Medicare and Social Security carries political risks. The eligibility age for full benefits is now gradually increasing. For those born after 1960, it will be 67. Romney would increase it further, allowing it to rise along with increases in longevity. He also would slow the growth in benefits somewhat for wealthier recipients.
"Romney's playing with fire. You always are when you delve into Social Security and Medicare," said Larry Sabato, director of the Center for Politics at the University of Virginia.
Yet this could be the year the conventional political rules change, because the skyrocketing federal debt is such an ominous threat to the nation's economic well-being.
The GOP plan, proposed in several similar formats, works generally like this: After 2022, seniors newly eligible for Medicare would get federal subsidies to buy insurance coverage. They could purchase that coverage from Medicare, but they would have the option of buying a policy from a private company.
All insurance plans would have to offer coverage "at least comparable to what Medicare provides today." If seniors wanted a more expensive plan, they would have to pay the difference between the federal aid and the premiums' price. No one currently 55 or older would be affected.
Should they pick a less expensive plan, they could use the leftover federal funds to pay other medical expenses, like co-pays and deductibles.
All sides agree that something has to be done to control Medicare costs and, to a lesser degree, Social Security. The report issued last month by the programs' trustees urged: "Lawmakers should not delay addressing the long-run financial challenges facing Social Security and Medicare."
Social Security's financial shortfall is less urgent; the trustees estimated that its trust fund reserves will be exhausted in 2033. After that, tax income would be enough to pay only about three-quarters of scheduled benefits through 2086.
Medicare's situation is more dire. The trustees estimated that the program's hospital insurance trust fund will be depleted by 2024.
Democrats' major strategy for cutting costs is the 15-member Independent Payment Advisory Board, created by the 2010 federal health care law. The board, appointed by the president and subject to Senate confirmation, would include physicians and patient advocates. It will recommend ways to save money. The law's provisions aim to strip about $480 billion from Medicare costs over the next 12 years.
Obama touted the commission last month as a panel "not made up of bureaucrats from government or insurance companies, but doctors and nurses and medical experts and consumers, who will look at all the evidence and recommend the best way to reduce unnecessary health care spending while protecting access to the care that the seniors need."
Republicans claim the panel would have too much power to make important medical decisions. It wouldn't, because its recommendations would be subject to congressional review. In March, though, the GOP-led House of Representatives voted to do away with it. That proposal is going nowhere in the Democratic-run Senate.
"You have two fundamentally different approaches," said Rep. Chris Van Hollen of Maryland, the top Democrat on the House Budget Committee.
More Nation & World Headlines
Cop indicted for murder in traffic-stop shooting Will ‘Happy Birthday’ song be free to use soon? Debris linked to missing Malaysian 777 Export-Import Bank excluded from highway bill 777 departs Aleutians after emergency landing House approves highway funding bill Taliban leader Mullah Omar dead, Afghans say Administration wants to give prisoners access to Pell grants
Our new comment system is not supported in IE 7. Please upgrade your browser here.